This clause tests whether it's argument is a floating point value or an integer, if the argument is of another type then the clause fails.
see also: atom/1 atomic/1 compound/1 float/1 instance/1 integer/1 nonvar/1 var/1
| Examples | |
| number("hello"). | fail |
| number(-10.1) | succeeds |
| number(9). | succeeds |
| X=10, number(X). | fail |